Solving Tailings Impoundment Water Balance Problems with the SVFlux 3D Seepage Software
By Murray Fredlund
June 22, 2007
This application of SVFlux involved the calculation of a water balance for a tailings facility close to Queensland, Australia. Flow past the earth dams had been measured in the field and the desire was to see if a numerical model could accurately predict the flow in a blind test.
The climate in the area is semi-arid with an annual rainfall of 702 mm/yr and a potential evaporation rate of 1650 mm/yr.
The tailings were hydraulically placed behind an engineered embankment 5.8 km long. In the middle of the tailings is a 100 ha pool. Overall the tailings covered an area of over 400 ha. Depths of the tailings ranged from 32m to 1m.
The tailings are subject to the water balance components of precipitation, evapotranspiration, infiltration, runoff, recharge, and seepage. They are also partially unsaturated which implies a certain non-linearity of flow.
Numerical modeling was difficult due to the highly irregular 3D geometry and the non-linearity of the unsaturated flow. It was also desired to couple in the calculation of actual evaporation.
A series of 1D and 3D numerical models were created in order to properly model the scenario. Specifically a three-zone 3D numerical model was used to represent the tailings facility. The modeling was successfully completed in under two weeks time and results matched the field measured results with an error of less than 5%.
The SVFlux software allowed reasonable solution to the water balance calculations in a faster-than-expected time period. I would recommend the product for this type of application.